Among the means for bettering the surface smoothness of paper are proper selection of pulp material, calendering of paper, increase of pressing force and increase of paper density. For enhancing the rigidity (stiffness) of paper, means are known such as properly selecting the pulp material, making the paper bulky, etc. However, the treatment for bettering the surface smoothness of paper and the treatment for enhancing the rigidity (stiffness) of paper are incompatible with each other, and thus it has been difficult to satisfy both requirements at the same time.